Step 1: Preheat the Oven
Start by preheating your oven to 375°F (190°C). Line a muffin tin with paper liners to make cleanup easier and ensure the muffins come out of the pan cleanly.

Step 2: Mix the Dry Ingredients
In a large bowl, whisk together the flour, granulated sugar, baking powder, baking soda, and salt. This ensures the dry ingredients are evenly combined and will distribute well throughout the batter.

Step 3: Mix the Wet Ingredients
In a separate bowl, whisk together the melted butter, fresh orange juice, milk, eggs, orange zest, and vanilla extract. The orange juice and zest provide the muffins with their vibrant flavor.

Step 4: Combine Wet and Dry Ingredients
Gradually add the wet ingredients to the dry ingredients, stirring gently until just combined. Be careful not to overmix; a few lumps are okay. Overmixing can make the muffins dense instead of light and fluffy.

Step 5: Fill the Muffin Cups
Divide the batter evenly among the prepared muffin cups, filling each about 2/3 full. This allows room for the muffins to rise without spilling over the edges.

Step 6: Bake the Muffins
Place the muffin tin in the preheated oven and bake for 18-20 minutes. The muffins are done when a toothpick inserted into the center comes out clean or with just a few moist crumbs.

Step 7: Cool the Muffins
Once baked, let the muffins cool in the tin for 5 minutes. After that, transfer them to a wire rack to cool completely. This prevents the muffins from becoming soggy as they cool.